This application claims the benefit under 35 U.S.C. § 119(a) of Korean Patent Application No. 2003-58502, filed on Aug. 23, 2003, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink cartridge used in an inkjet recording apparatus.
2. Description of the Related Art
FIG. 1 schematically shows a conventional ink cartridge as disclosed in U.S. Pat. No. 5,877,794.
Referring to FIG. 1, an ink tank 2 and a print head 1 are shown. The ink tank 2 is divided into a main ink chamber 4 containing ink 3 and an auxiliary ink chamber 6 filled with a porous member 9. The main ink chamber 4 communicates with the print head 1 via a first opening 5. The auxiliary ink chamber 6 communicates with the main ink chamber 4 via a second opening 7. The auxiliary ink chamber 6 has an air vent 8. The porous member 9 absorbs the ink 3 through the second opening 7 by capillary action, which maintains the inside of the ink tank 2 to be in a negative pressure state where the internal pressure of the ink tank 2 is lower than the external pressure.
The ink 3 in the main ink chamber 4 is supplied into the print head 1 via the first opening 5 and then ejected from the print head 1. As the ink 3 is consumed, the internal pressure of the main ink chamber 4 decreases. At this time, air coming in through the air vent 8 is introduced into the main ink chamber 4 through the porous member 9. That is, the porous member 9 serves as a pressure buffer between the inside and outside of the main ink chamber 4 by creating capillary pressure.
Ink in an ink cartridge is affected by variations in environmental pressure and temperature. In particular, when environmental temperature and pressure change during transportation, leakage of the ink 3 from the print head 1 or the air vent 8 may occur. For example, in the case of transportation via an airplane in which the environmental pressure can be about 0.7 atmospheres, the internal pressure of the main ink chamber 4 can be higher than the external pressure. Also, in a case where a ship carrying an ink cartridge-containing container transits the equator, the temperature inside the container rises to about 60 to 70 degrees Celsius and the air inside the main ink chamber 4 expands. As a result, the internal pressure of the main ink chamber 4 becomes higher than the external pressure, thereby causing a leakage of the ink 3 from the print head 1 or the air vent 8. The leakage of the ink 3 may also be caused when an ink cartridge is used in adverse conditions in which the internal pressure and the external pressure of the main ink chamber 4 can be reversed. Such leakage of the ink 3 may contaminate the exterior of an ink cartridge and cause high consumption of the ink 3.